Electromagnetic contactor

ABSTRACT

An electromagnetic contactor with a magnetic core subdivided into two portions, wherein the first of said portions is mounted fixedly with respect to the operative closure stroke of the contactor, but with no positive connection to the contactor structure so as to move back under impact of the second core portion at the time of contactor closure. Said first core portion may be manually lifted for disengaging and removing the driving coil of the contactor.

[451 Jan. 2, 1973 541 ELECTROMAGNETIC CONTACTOR 3,458,838 335/1323,383,634 5/1968 Bauer et al. ..........................335/257 [75]Inventor: Alflo Caltabiano, Turin, ltaly [73] Assignee: Ghisalba S.p.A.,Turin, Italy Primary Examiner-Harold Broome Attorney-Irvin S. Thompsonand Robert J. Patch [22] Filed: July 7, 1971 [21] App]. No.: 160,438

ABSTRACT An electromagnetic contactor with a magnetic core 30 F0 n Acat- Prio D ta subdivided into two portions, wherein the first of said 1relg W n y a portions is mounted fixedly with respect to the opera- Oct22, 1970 Italy.........................................705l4 rive losurestroke of the contactor, but with no positive connection to thecontactor structure so as to /2 move back under impact of the secondcore portion at [51] Int. ......H0111 50/18 the time of contactorclosure. Said first core portion [58] Field of may be manually liftedfor disengaging and removing the driving coil of the contactor.

8 Claims, 4 Drawing Figures References Cited UNITED STATES PATENTS3,196,231 Meyer PAIENTEDJAN' 2191 3.708.769

SHEET 2 [IF 2 I INVENTOR 44 Ava CALTAB/fl/VO ATTORNEYS BACKGROUNDOF'TI-IE INVENTION This invention refers to an electromagnetic contactorwherein improvements are made with the purpose of reducing core wear andtendency to bounce, of improving the closure power and of making easiermounting and dismounting the driving coil or coils.

In those electromagnetic contactors wherein the fixed portion of themagnetic core is stiffly connected" sequent contact damage.

In certain known contactors, said detrimental events have been somewhatreduced by connecting the fixed core portion to the contactor structurethrough yielding members capable of subduing up to a certain extent theimpact of themovable core portion. Even in such contactors, however, theimportance of .the above-mentioned detrimental events remains such as toproduce fast wear and sometimes serious drawbacks.

Another disadvantage of a completely different kind,

which is found in most known electromagnetic contac tors, is thedifficulty in mounting and dismounting the driving coil. Except forcomplicated and expensive arrangements, which sometimes producedisadvantages in operation, there is no means of replacing the coilwithout dismounting other members of the contactor too, as for examplethe unit of the movable contacts or the magnetic core. Therefore,contactors without coil, and coils of different characteristics to bemounted on demand according to the requirements of users, cannot beseparately stored, as it would be of advantage for organization.Furthermore, when the contactor is in use, the"replacemer 1t of thecoil, which is subjected to burnings, requires mostly disconnection ofthe feeding bars and thus a-ra'ther long operation during which all theappliance comprising the damaged contactor remains inactive.

BRIEF SUMMARY OF THE INVENTION This invention has the object ofimproving an elec tromagnetic" contactor by introducing therein apeculiarity suitable by itself for reducing in a substantial 'manner allthe above stated disadvantages of different kinds of the knowncontactors, even by improving the closure power and without in any wayincreasing the manufacture costs.

-According to the invention, this object is attained by the fact thatthe socalled fixed portion of the magnetic core has no actual connectionto the contactor structure, but it is simply supported in the restposition, when the contactoris .open, by a one-sided bond capable ofpreventing said fixed portionfrom approaching the movable core portion,but unable to oppose a noticeable resistance to a displacement of saidsocalled fixed portion of the core in a direction opposite said movableportion. Of course, the fixed portion of the core is so called only withreference to its operation stroke. In this manner, when the contactorcloses and the movable core portion comes to contact with the fixed coreportion, this latter yields due to the impact of the movable portion,without any resistance except its own inertia, and it moves back.Therefore the movable core'portion joined with the fixed portioncontinues to a-certain extent itsstroke beyond the normal closureposition, up to exhaustion of its own kinetic energy and.

then, always joined with the fixed core portion, the movable portionreturns'towards the normal closure position, without having caused anyviolent impact, noise or vibration. Both the core wear and the tendencyto contact bounce are therefore substantially reduced. Furthermore, whenthe movable core portion effects the said additional stroke, it beingconnected as known to the driven unit of movable contacts, it loadesbeyond the normal value the springs of the movable contacts and thus itpushes said movable contacts against the fixed contacts, during a brieflapse of time after contactor closure, with an increased load. On onehand said increased load further reduces the bounce tendency, and on theother hand it gives rise to an unusual adherence between the contactsduring the peak of maximum current absorption which immediately followsthe contactor closure, thus increasing the closure power of thecontactor, if all other features remain unchanged.

Finally, it becomes possible to allow manual retraction of the fixedcore portion from its rest position to an extent sufficient fordisengaging the magnetic core from the driving coil. By making the coilremovable from the front portion of the contactor structure, between themovable contacts, it then becomes possible to mount and dismount thecoil orcoils from the installed contactor by a simple and easyoperation, without requiring dismounting of any other portion of thecontactor.

BRIEF DESCRIPTION OF THE DRAWINGS This invention will be more clearlyunderstood from the following description, drawn up with reference to anon limitative example of embodiment which is diagrammatically shown theannexed drawings. In the drawings:

- FIG. 1 shows a vertical section'of the contactor, I taken along thedisplacement direction of the movable contact unit and according to thebroken line I-I of FIG. 2;

FIG. 2 is a rear'view of a section of th'econtactor, taken along theline II-II of FIG. Ii

FIG. 3 is a partial section similar to FIG. 1 but showing the fixed coreportion in retracted position and the driving coil during its extractionoperation;

FIG. 4 is a partial front view showing the respective positions of thecoils and themovable contacts.

DETAILED DESCRIPTION members 4 are carried, under action of springs 5,by a movable unit 6 which passes through openings 7 of the intermediatewall 1 and which is pin connected, at the rear end thereof, to squarelevers 8. Said square levers 8 are hinged to pivots 9 fixed to thecontactor structure 0, and at the opposite ends they are connected tothe movable portion 10 of the magnetic core. Said movable portion 10faces the socalled fixed portion 11 (which however, as alreadyexplained, may be considered fixed only with reference to the mainoperation stroke). The driving coils 12, which in the example are innumber of two, are linked to the branches of the fixed and movableportions 11 and 10 of the magnetic core. Near the fixed and movablecontact members 3 and 4, on the cover 2 acting as a firescreen aremounted arc extinguishing plates 13. All the component parts describedtill now, as well as their arrangements and functions, are well known tothose skilled in the art, and therefore they do not require a moredetailed description.

In the known contactors, the fixed portion 11 of the magnetic core isfixed, stiffly or through shock-absorbing members of a somewhatyieldable material, to the contactor structure 0.

According to this invention, on the contrary, the socalled fixed portion11 of the magnetic core has no fixed connection to the contactorstructure, but it is guided with respect to said structure so that itmay move in the same direction of displacement as the movable portion 10of the magnetic core, along a sufficiently long stroke, but only in thedirection of departing from said movable portion 10 and not in thedirection of approaching it from the rest position. This has beenpractically obtained, in the shown example, by providing the fixedportion 11 of the magnetic core with extensions 14 inserted within guidemembers 15 fixed to the structure 0 and whose shape, which according tothe shown example is like a -U-, allows the socalled fixed member 11 todisplace only in the same direction of the operation closure stroke ofthe movable core portion 10. Moreover said guide members 15 limit themobility of the socalled fixed portion 11 such as to establish a restposition thereof. Said fixed portion 11 is maintained in its restposition by its own weight or, if needed, by action or with the aid oflight return springs, not shown. Preferably, the extensions 14 engagethe guide members 15 by means of pads 16 of a shock-absorbing orsomewhat yieldable material, such as rubber, nylon or the like.

The contactor operation takes place as follows. When the coils 12 arefeeded in view of producing closure of the contactor, a magnetic flux isproduced in the magnetic circuit comprising the movable and fixedportions 10 and 11 of the magnetic core, and as a consequence anattraction force is applied onto the fixed core portion 11, in thedirection downwards according to the drawing, as well as onto themovable core por tion 10, in the direction upwards according to thedrawing. Since the extensions 14 rest through the pads 16 upon thetransverse portion of the guide members 7 15, the fixed core portion 11may not move under action of said attraction force which trends toapproach said fixed portion 11 to the movable portion 10. As aconsequence, during this phase of operation the fixed core portion 11behaves in the same manner as in the known contactors, wherein it isfixedly connected to the contactor structure.

On the other side, the movable core portion 10 is displaced upwards(according to the drawing) by said attraction force and, in a well knownmanner, it causes the square levers 8 to rotate about the pivots 9 andthe movable unit 6 to displace (towards the left hand side, according tothe drawing) thus approaching the movable contact members 4 to the fixedcontact members 3 up to contact thereof, and then compressing thesprings S of the movable contact members 4.

When the movable core portion 10 takes contact with the fixed coreportion 11, it has at this time a somewhat reduced speed due to theabsorption of a portion of the kinetic energy by action of thecompression springs 5, however the speed of said movable core portionstill is noticeable. However the impact against the so-called fixed coreportion 11 does not stop the movable core portion 10, thus dissipatingits kinetic energy into vibrations, noise and heat produced by anelasticdeformations of the materials, as in the known contactors the socalledfixed portion 11 of the core moves back, joined with the movable coreportion 10, thus allowing the latter to travel along an additionalstroke beyond its normal closure position. During said additionalstroke, the contact springs 5 are further compressed, and so the returnsprings of, the movable unit 6, if they are provided as required in somecontactor types, but not shown in the example. Compression of saidsprings exhausts the whole kinetic energy of the movable core portion10. Thereafter, under return action of the compressed springs, themovable unit 6, the movable core portion 10 and the socalled fixed coreportion 11 return towards the normal closure position and stop when theextensions 14 of the socalled fixed core portion 11 rest anew upon thetransverse portion of the guide members 15. At this time the somewhatyieldable pads 16 absorbe the light shock which is produced.

Of course, the impact between both core portions when they take contactis substantially less severe than in the known contactors, since it ishere supported only by the own inertia of the socalled fixed coreportion 1 1. There is consequently a substantial reduction in theanelastic deformation which progressively damages the component parts ofthe contactor, with special reference to the magnetic core portions, andnoise, vibrations and tendency to contact bounce are also considerablyreduced. During the following additional stroke, the increasedcompression of the springs 5 further hampers the tendency to the contactbounce and moreover it produces an increased contact pressure betweenthe movable and fixed contact members during the period of time,immediately following the contact closure, wherein there is generally apeak of maximum current absorption through the contactor, Therefore theclosure power of the contactor is increased by unchanging otherconditions.

Of course, the above stated advantages are obtained independently fromthe mounting manner of the coils 12 which therefore, as long as thereduction of the closure impact is concerned, may be of any kind andanyhow mounted. However, it is possible to take advantage of the statedfeature of the so-called fixed magnetic core portion 11 being movablymounted instead of being fixed to the contactor structure 0, for furtherallowing easy mounting and dismounting of the driving coil or coils.

There is no absolute need for limiting the possible extension ofmovement of the socalled fixed core portion 11 in the direction ofallowed displacement, however it is suitable to provide such alimitation, for example by means of a stop 17, for avoiding the fixedcore portion leaving its place during transportation or as a consequenceof a wrong manual operation. For operation purposes, the displacementstroke allowed to the fixed core portion may amount to only fewmillimeters, for example ten millimeters. On the contrary, the stop 17is arranged as such a distance a from the fixed core portion, as toallow a displacement amounting at least to the difference between theheight L of the coil 12 and the length T of the air gap provided in themagnetic core circuit, in open position. Moreover, the coil or coils l2driving the contactor are arranged within suitable windows 71' of theintermediate wall 1; they are fixed in front of said wall, at 18, 19 andare arranged (as shown in FIG. 4) in the free spaces between the movablecontact members 4 of the contactor. If said requirements are fulfilled,it is sufficient to release the connections 18, 19 and to raise thefixed core portion 11 up to against the stop 17 for allowing removal ofthe coils 12 from the front side of the contactor, by passing thembetween the movable contact members 4 as diagrammatically shown in FIG.3. Dismounting the coils, as it appears, requires the simple removal ofthe firescreen or cover 2 with the affixed arc-extinguishing plates 13,without requiring dismounting of any other component part of thecontactor, even if it is installed. Since the operation is effectedentirely from the front side, it founds no hindrance in other applianceswhich may be installed in the vicinity. As a consequence dismounting thecoils is extremely easy, thus affording the already stated advantages.

According to the shown form of embodiment, the movable core portion isslightly engaged within'the coils 12-, and therefore said coils shouldbe slightly raised for disengaging them from the magnetic core when theyhave to be removed. It is possible, however,

to arrange the'movable pore portion-as at 10' (FIG. 2), i.e.normallydisengaged from the coils 12, thusavoiding need for raising thecoils before removal thereof.

, The electric connection of the coils 12 may take place, in a mannerper se known, by means of their own mechanic connection, thus making'theoperation still easier. Raising the fixed core portion may be effectedby acting from the front side of the contactor by means ofa'screw-driver or like suitable tool, and by operating onto a suitableextension 20 of the fixed core portion 11. I

Return of the fixed core portion 11 to its normal position may beeffected by its own weight or by a return spring (not shown) which,however, should apply a sufficiently light effort such as not to hindermanual raising of the fixed core portion nor its going back at the timeof impact against it of the movable core portion 10.

It is to be noted that the characteristic feature according to theinvention is actually suitable for attaining the desired advantages yetwithout involving an increased cost or a complication in the manufactureof the concerned contactor, so that its application involves aconsiderable technical and industrial advantage.

The shape and the arrangement of the different component parts "of thecontactor may, of course, .be modified in different ways with respect tothe shown example of embodiment, without departing from the scope of theinvention.

Having thus described my invention, what I claim is:

1. An electromagnetic.contactor comprising a structure, mounted in saidstructure at least one driving coil, a first magnetic core portionmounted in said structure for movement in a stroke direction andmagnetically linked with said driving coil, a movable unit guided insaid structure and operatively connected to said first core portion,movable contact members carried by said movable unit, fixed contactmembers mounted on said structure and cooperable with said movablecontact members, a second magnetic core portion linked with said drivingcoil and cooperable with said first core portion, and guide membersinterposed between said structure and said second core portion andsupporting said second core portion in a rest position, said guidemembers guiding said second core portion along a direction of movementcorresponding to said stroke direction of said first core portion andallowing free displacement without noticeable resistance of said secondcore portion from said rest position thereof only in the direction ofdeparting from said first core portion, whereby upon feeding of saidcoil the first core portion moves towards thesecond core portion bydriving said movable unit and closing together said fixed and movablecontact members, and upon impact of the first core portion the secondcore portion moves back thus allowing an additional stroke of the firstcore portion, and finally returns with said first core portion to therest position.

2. An electromagnetic contactor as set forth in claim 1, wherein saidguide members are U-shaped and have transverse portions, and whereinsaid second core portion has extensions engaged in said guide members,

said extensions resting upon said trasverse portions of the guidemembers in the open position of the contactor and during a first portionof the closure operation.

'3. An electromagnetic contactor as set forth in claim 1, wherein saidguidemembers are U-shaped and have transverse portions, said second coreportion has extensions engaged in said guide members, and pads of asomewhat yieldable material are inserted between each extension of thesecond core portion and each transverse portion of the guide members.

4. An electromagnetic contactor as set forth in claim 1, furthercomprising a stop cooperable with said second core portion in view oflimiting the length of the displacement allowed thereto.

5. An electromagnetic contactor as set forth in claim 1, furthercomprising a stopcooperable with said second core portion, said stopbeing arranged at a distance from the rest position of the second coreportion, at'least equal to the difference between the height of saiddriving coil and the distance between both said first and second coreportions in the open position of the contactor, whereby upon displacingsaid second core portion up to against said stop, said driving coil canbe disengaged form both the first and second core portions and removed.

6. An electromagnetic contactor as set forth in claim 1, wherein saidstructure comprises an intermediate wall, said intermediate wall haswindows apertured therein in correspondence with free spaces betweensaid fixed contact members, said driving coil or coils are inserted insaid windows from the front part of the contactor through said freespaces between the fixed contact members, and connection membersoperable from the front part of the contactor are provided for betweensaid structure and said driving coil or coils.

7. An electromagnetic contactor as set forth in claim l

1. An electromagnetic contactor comprising a structure, mounted in saidstructure at least one driving coil, a first magnetic core portionmounted in said structure for movement in a stroke direction andmagnetically linked with said driving coil, a movable unit guided insaid structure and operatively connected to said first core portion,movable contact members carried by said movable unit, fixed contactmembers mounted on said structure and cooperable with said movablecontact members, a second magnetic core portion linked with said drivingcoil and cooperable with said first core portion, and guide membersinterposed between said structure and said second core portion andsupporting said second core portion in a rest position, said guidemembers guiding said second core portion along a direction of movementcorresponding to said stroke direction of said first core portion andallowing free displacement without noticeable resistance of said secondcore portion from said rest position thereof only in the direction ofdeparting from said first core portion, whereby upon feeding of saidcoil the first core portion moves towards the second core portion bydriving said movable unit and closing together said fixed and movablecontact members, and upon impact of the first core portion the secondcore portion moves back thus allowing an additional stroke of the firstcore portion, and finally returns with said first core portion to therest position.
 2. An electromagnetic contactor as set forth in claim 1,wherein said guide members are U-shaped and have transverse portions,and wherein said second core portion has extensions engaged in saidguide members, said extensions resting upon said trasverse portions ofthe guide members in the open position of the contactor and during afirst portion of the closure operation.
 3. An electromagnetic contactoras set forth in claim 1, wherein said guide members are U-shaped andhave transverse portions, said second core portion has extensionsengaged in said guide members, and pads of a somewhat yieldable materialare inserted between each extension of the second core portion and eachtransverse portion of the guiDe members.
 4. An electromagnetic contactoras set forth in claim 1, further comprising a stop cooperable with saidsecond core portion in view of limiting the length of the displacementallowed thereto.
 5. An electromagnetic contactor as set forth in claim1, further comprising a stop cooperable with said second core portion,said stop being arranged at a distance from the rest position of thesecond core portion, at least equal to the difference between the heightof said driving coil and the distance between both said first and secondcore portions in the open position of the contactor, whereby upondisplacing said second core portion up to against said stop, saiddriving coil can be disengaged form both the first and second coreportions and removed.
 6. An electromagnetic contactor as set forth inclaim 1, wherein said structure comprises an intermediate wall, saidintermediate wall has windows apertured therein in correspondence withfree spaces between said fixed contact members, said driving coil orcoils are inserted in said windows from the front part of the contactorthrough said free spaces between the fixed contact members, andconnection members operable from the front part of the contactor areprovided for between said structure and said driving coil or coils. 7.An electromagnetic contactor as set forth in claim 1, wherein in theopen position of the contactor said first core portion is disengagedfrom said driving coil or coils.
 8. An electromagnetic contactor as setforth in claim 1, wherein said second core portion has an extensionoperable with the aid of a suitable tool from the front part of thecontactor for manually raising said second core portion.